| Actually, I wonder if we can put the check in just one spot: coreView.
| Whenever we use coreView, we're about to inspect a type. And we should
| never be inspecting a metavariable in this way.
Yes, that's right. Maybe that makes a useful distinction between coreView and tcView; the former should never see a meta-variable.
I'm not sure we are fully consistent on when we call each, but it'd be a good start.
Go for it
Simon
| -----Original Message-----
| From: Richard Eisenberg [mailto:rae@cs.brynmawr.edu]
| Sent: 20 October 2017 22:44
| To: Simon Peyton Jones
| Cc: ghc-devs
| Subject: splitting metavariables
|
| Hi Simon,
|
| I just commented
| (https://ghc.haskell.org/trac/ghc/ticket/14331#comment:35) about a
| situation where we call splitFunTys on a type that might be a
| metavariable. (You don't have to read the comment -- that's just to
| set the context.) Now that I think of it, we should never call the
| splitXXX functions on metavariables -- any time we do so is wrong. I
| suppose it's OK if we, say, call splitTyConApp_maybe on (T alpha beta
| gamma), because we never look through the metavariables there. But it
| can't possible be write to call splitTyConApp_maybe on alpha.
|
| Do you agree? Should we ASSERT that we don't do this?
|
| The tcXXX variants are no different in this regard.
|
| Actually, I wonder if we can put the check in just one spot: coreView.
| Whenever we use coreView, we're about to inspect a type. And we should
| never be inspecting a metavariable in this way.
|
| Richard
